Economic and environmental demands on gear oil compositions means that they are being pushed to their performance limits. The choice of the combination of base stock and additive package is crucial. In particular, additives are required to reduce friction. A wide range of friction reducing additives are currently used commercially in gear oils such as esters, partial esters, phosphonates, organomolybdenum-based compounds, fatty acids, higher alcohols, fatty acid esters, sulfur containing esters, phosphate esters, acid phosphoric acid esters, and amine salts of phosphoric acid esters. However, these materials can have drawbacks such as water entrainment/emulsification and/or foaming; and/or insufficient friction reduction, seal compatibility, paint compatibility, thermal and/or oxidative stability. Thus, there is a need for improved friction reducing additives in gear oils, particularly for use in automotive, marine and in industrial applications such as in mining; paper, textile and sugar mills; steel production and in wind turbines.